For the past decades, nanomaterials have been attracted for their excellent properties to overcome many difficulties in various research fields. Nano-engineering has a potential in a wide range of applications, including energy storage and transformation, display devices, biomedical imaging and other bio-related applications, data storage media, sensors and other electronic devices, and catalysts.
Recently, researchers have been interested in nanometer-sized tantalum oxide due to their unique properties. For example, tantalum oxide has a better electrical insulation capability, comparing with silica, and is considered as a good candidate for highly dielectric material. In addition, tantalum oxide is ideal material for an anti-reflective coating, a water-splitting catalyst, a fixed metal oxide catalyst and an X-ray contrast agent, due to its high refractive index, thermal and chemical stability, catalytic activity, radiopacity and biocompatibility.
Synthesis and application of tantalum oxide nanoparticles are very important. Nanoparticles with high uniformity and excellent dispersibility in many solvents are required to produce solution-processed electronic and optical devices. Synthesis of mono-disperse nanoparticles capped with suitable stabilizing molecules make it possible to prepare a defect-free film comprised of nanoparticle layers. Moreover, it is very important in a biomedicinal field to developing an easy surface-modifying process. For these purposes, the surface of a nanoparticle should be modified to have functional moieties including antifouling agents, drugs, organic dyes and antibodies, which give colloidal dispersibility and multi-functionality to the nanoparticle.
Meanwhile, derivatives of iodobenzoic acid have been used as X-ray CT contrast agents until now, in spite of their danger and side effects due to iodide. However, it is known that the derivatives of iodobenzoic acid have low molecular weight and are rapidly excreted via renal elimination, resulting in short circulation time that limits their applications for targeting lesions. In addition, many patents disclose the use of gold nanoparticles for X-ray CT contrast agents. However, these gold nanoparticles are not economical. WO 2008/092059 (Korean Patent Application Publication No. 10-2009-0108697) discloses an X-ray CT contrast agent using tantalum oxide nanoparticles. However, there has not yet been any report on surface-modified mono-disperse tantalum oxide nanoparticles, method for simple and low-cost large-scale production thereof and uses of the same.